Cylinder blocks consisting of hypoeutectic aluminum alloys cannot provide running surfaces of adequate wear resistance for cast iron piston rings. Current practice for obtaining the required wear resistance is to cast or press gray cast iron cylinder liners into such cylinder blocks. However, for recycling purposes, gray cast iron cylinder liners which are cast into cylinder blocks of hypoeutectic aluminum alloys make it difficult to melt worn blocks and return these to the aluminum production cycle. On the other hand, gray cast iron cylinder liners which are pressed into cylinder blocks of hypoeutectic aluminum alloys must be removed by means of an expensive drawing operation before worn blocks can be melted and returned to the aluminum-production cycle.
If the blocks and their ferrous components are shredded, an additional separating procedure must be performed before worn blocks can be melted.
Cylinder blocks of hypoeutectic aluminum alloys can also be galvanically coated with wear-resistant running surfaces (trade name "Nikasil"). However, this requires galvanic treatment with a relatively large number of cleaning, covering and immersing operations.
Further known are cylinder blocks of hypereutectic aluminum alloys in which wear-resistant running surfaces can be produced by honing and etching in order to partially expose primary silicon particles present in the material. These cylinder blocks are capable of being recycled as desired and provide good results as regards the wear resistance of their running surfaces.
Another method of making cylinder blocks having silicon particles at the running surfaces involves the use of compressed preforms containing ceramic fibers. Prior to casting of a cylinder block, the preforms are placed in the mold. When the mold is filled with a hypoeutectic aluminum alloy, the preforms are infiltrated so that a fibrous surface having the desired wear resistance is obtained. This method has the disadvantage that an additional manufacturing operation is required for the special preforms.